1. Field of the Invention
The present invention relates to a loudspeaker damper serving as a supporting system of diaphragm and a loudspeaker using the damper.
2. Description of the Related Art
A structure of a conventional loudspeaker and a loudspeaker damper will be described. FIG. 1 is a cross-sectional view showing a structure of a loudspeaker using a conventional damper. As shown in FIG. 1, the loudspeaker includes a voice coil bobbin 1, a diaphragm 2, a damper 3P, an edge 4 and a frame 5. A reference letter Z shown in FIG. 1 indicates a direction that the voice coil bobbin 1 vibrates during operation of the loudspeaker, and a reference letter R indicates a direction perpendicular to the Z direction, i.e., a radial direction of loudspeaker.
A voice coil 1a is wound around a lower portion of the voice coil bobbin 1. The voice coil bobbin 1 is elastically held, together with the diaphragm 2, at the frame 5 by the damper 3P. An outer peripheral portion of the diaphragm 2 is supported to the frame 5 by the edge 4 so as to vibrate. A magnet 6, a yoke 7 and a plate 8 constitute a magnetic circuit and a magnetic flux is generated at a magnetic gap 9. When a signal current is applied to the voice coil 1a placed within the magnetic gap 9, the voice coil bobbin 1 vibrates, by means of the magnetic flux of the magnetic gap 9, in the Z direction with a driving force which is proportional to the signal current. The vibration is transmitted to the diaphragm 2, so that sound is radiated.
In accordance with such a conventional loudspeaker, in order to vibrate the voice coil bobbin 1 and the diaphragm 2 so as to follow a signal current, a cross-sectional shape of the damper 3P is formed in a wavy shape. Further, a radial direction of the damper is expandable and contractible. In this way, the damper 3P easily vibrates in the Z direction.
In the case where the damper 3P has a wavy cross-sectional shape, the damper 3P easily vibrates also in the R direction. Ideally, the voice coil bobbin 1 and the diaphragm 2 vibrate only in the Z direction in proportion to a signal current. In accordance with an actual loudspeaker, however, vibration in the R direction as well as the Z direction is induced due to variations in assembling of the loudspeaker and weight balance, and force applied to the loudspeaker depending on an installation method.
Vibration in the R direction is referred to as a rolling phenomenon. If the rolling phenomenon occurs, the voice coil 1a abuts the yoke 7 or the plate 8 at a time of operation of the loudspeaker, so that unpleasant noise is generated or the voice coil 1a is broken. If the magnetic gap 9 is broaden in order to prevent such abutment of the voice coil 1a, an efficiency of electro acoustic conversion of the loudspeaker is reduced. Accordingly, if the rolling phenomenon can be suppressed while maintaining a distance of the magnetic gap 9 at a predetermined value, generation of unpleasant noise and failure of the voice coil 1a can be prevented and a high performance loudspeaker with high efficiency can be realized.
A loudspeaker damper of the present invention is configured by an annular member so as to have a central opening portion, and is provided with an outer peripheral waveform portion which has at least one concave or convex annular waveform at an outer peripheral portion, an inner peripheral waveform portion which has at least one concave or convex annular waveform at an inner peripheral portion, and a flat portion which is provided between the outer peripheral waveform portion and the inner peripheral waveform portion and has an annular flat surface.
A loudspeaker of the present invention is provided with a loudspeaker frame, a diaphragm which has an outer peripheral portion held by the loudspeaker frame so as to vibrate and applies aerial vibration, a cylindrical voice coil bobbin which is coupled to an inner peripheral portion of the diaphragm, a voice coil which is wound around the voice coil bobbin, a magnetic circuit which applies an electromagnetic force to the voice coil and a damper which has an outer peripheral portion held by the loudspeaker frame so as to vibrate and holds the voice coil bobbin so as to axially vibrate.